This invention relates to an adhesive sheet which when applied to an article will leave a mark on that article indicating that it has been applied and that it was subsequently removed from that article.
Before the present invention, two types of adhesive sheet designed to achieve the above result had been known to the art. The first type of adhesive sheet contained a supporting sheet made of a fragile material. An adhesive layer was coated on the rear surface of the fragile supporting sheet, as has been disclosed in U.S. Pat. No. 4,268,983. The second type of adhesive sheet designed to accomplish the above purpose, comprised a supporting sheet with a release agent applied to scattering portions of its rear surface. The entire rear surface of the supporting sheet was then coated with a metallic vapor deposition layer which in turn was coated with an adhesive layer. Both types of adhesive sheets known to the art may be used for identification, authentication, sealing and other purposes when applied to products, containers or identification cards. When the adhesive sheet mode comprising a supporting sheet of a fragile material is peeled from a product or container, the fragile supporting sheet is partially broken and a portion of that fragile supporting sheet remains on the surface of the product or container. When the adhesive sheet containing a metallic vapor deposition layer is removed from a product or container, broken parts of that metallic vapor deposition layer remain on the surface of the product or container. Thus, for both types of adhesive sheet the presence of a residue of the sheet or metallic vapor deposition layer on the product or container indicates that the adhesive sheet had been applied and was subsequently removed therefrom.
However, both types of adhesive sheet suffer from a serious drawback. Specifically, the residual parts of the sheet or metallic vapor deposition layer left behind on the product or container may be wiped away completely, thus removing any indication that the adhesive sheet had been applied and then peeled away. The principal purpose of the present invention is to provide an adhesive, sheet which does not suffer from this defect which plagues conventional adhesive sheets, but will indicate the fact that adhesive sheet has been removed even if residual parts of the sheet have been wiped away from the product or container.